To perform studies on: physico-chemical and biological investigations of collagen and other natural macromolecules present in the blood vessel walls in order to elucidate those parameters that are responsible for the initiation of blood clotting and platelet aggregation and adhesion; and chemical modifications of collagen and other natural macromolecules present in the blood vessel walls aimed at transforming these molecules into either blood compatible surface coatings or blood compatible bulk materials.